The invention relates to an electric drive system, in particular for an electrically operated vehicle such as an electric car or a hybrid vehicle.
As is depicted in FIG. 1 by way of example, multiphase current is fed in an electric drive system 100 into an electric machine 101 typically by means of an inverter 102 in the form of a pulse width modulated inverter. To this end, a DC voltage provided by a DC voltage intermediate circuit 103 can be converted into a multiphase AC voltage, for example a three-phase AC voltage. The DC voltage intermediate circuit 103 is fed by a string consisting of series-connected battery modules 105 or any desired DC voltage sources.
In order to be able to meet the requirements for power and energy given for a respective application, a plurality of battery modules or battery cells are frequently connected in series in an energy storage system. If however high power outputs are required from the electric machine, it may be necessary to take measures in implementing the electric drive system 100 that meet the increased power output requirements.
It can, for example, be possible to connect a plurality of strings 104 consisting of series-connected battery modules 105 in parallel. This can however lead to undesired compensation currents between the strings 104.
In addition, it may also be necessary to increase the current carrying capacity of the components of the inverter 102 and the electric machine 101. Alternatively, the intermediate circuit voltage could also be raised. In any case, extensive adaptations and changes in the implementation of the electric drive system will be necessary, which in turn lead to increased implementation effort and costs.
The American patent publication US 2007/0070667 discloses a drive system for an electrically operated vehicle comprising multiple inverters connected in parallel, which supply AC voltage to a multiphase motor. The German patent publication DE 10 2011 085 731 A1 discloses an electric drive system for a six-phase motor comprising two inverters connected in parallel. The German patent publication DE 10 2008 008 978 A1 discloses modular drive converters. The German patent publication DE 10 2010 001 250 A1 discloses an electric drive system for an electric machine comprising two phase systems, which are fed via separate inverters.